Post traumatic stress disorder (PTSD) is associated with a wide range of negative long-term consequences, including problems with interpersonal relationships, higher rates of unhealthy behaviors, physical problems, and mortality (Tanielian &Jaycox, 2008). Although everyone is at some risk of exposure to traumatic events that precipitate PTSD, a burgeoning literature suggests there are significant disparities in PTSD risk, especially for racial-ethnic minorities (e.g., Pole et al., 2008) and women (e.g., Olff et al., 2007;Tolin &Foa, 2006). For example, Latinos are thought to be at both high risk of trauma and PTSD (Eisenman et al., 2008). Women have both a higher overall prevalence of PTSD (10.4% vs. 5.0%) and are much more likely to develop PTSD in response to particular traumas like physical assault (Kessler et al., 1995). Individuals with PTSD report more barriers to care than those without the disorder (Amaya- Jackson et al., 1999), and certain subgroups may experience more barriers than others (Boscarino et al., 2005;Jaycox et al., 2004). Despite the availability of effective treatments for PTSD (Foa et al., 2000;Ursano et al., 2004;VA/DoD 2004;NICE, 2005), including pharmacological treatment, psychotherapeutic treatment, and education and support services, many do not seek treatment or they substantially delay treatment seeking. Even when those with PTSD do receive care, it may be inadequate (Frueh et al., 2006;Wang, Lane et al., 2005). Yet, little is known about racial-ethnic and gender variation in trauma and mental health service use. This study seeks to 1) identify where needs are greatest by examining racial-ethnic and gender disparities in exposure to trauma and development of PTSD;2) examine racial-ethnic and gender disparities in access to mental health care by exploring perceived barriers to mental health care for those with PTSD;and 3) describe mental health service utilization patterns among racial-ethnic and gender groups with PTSD. The study is guided by Ronald Andersen's (1995) Behavioral Model of Health Services Use and employs the Collaborative Psychiatric Epidemiology Surveys data. These data contain 20,013 diagnostic interviews, and 1,194 of those interviewed met criteria for PTSD at some point in their lives. This is the first national data with enough power to investigate cultural influences on mental health (Colpe et al., 2004), and no studies have yet been published that focus on PTSD in the combined data. Eliminating health disparities is a fundamental goal of public health research and one of the main focuses of Healthy People 2010. This research aims to alleviate racial-ethnic and gender disparities in posttraumatic stress disorder (PTSD) by exploring variation in trauma exposure and subsequent PTSD, barriers to mental health care, and differences in utilization of mental health services. Findings from this research will help alleviate disparities in PTSD by identifying populations with higher burdens, better targeting and improving the outcomes of prevention and intervention, preparing providers to better care for populations experiencing disparities, and suggesting implications for funding that addresses health disparities.